Pump

ABSTRACT

A centrifugal pump for a kitchen appliance has a pump head and a pump body having a motor. The stator of the motor has a stator core, windings and an end cap fixed to one side of the stator core. The pump head has a volute and an impeller. The volute has a chamber with an inlet and an outlet. The chamber has an opening facing the pump body. The end cap is made of thermally conductive material and has an annular sidewall and a base plate. The sidewall surrounds the stator core. The base plate seals the opening of the chamber. Heat generated by the stator is transferred to liquid in the chamber via the end cap to cool the motor and to heat the liquid.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201310346613.6 filed in The People's Republic of China on Aug. 9, 2013, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a centrifugal pump and in particular, to a centrifugal pump for using in kitchen appliances such as dishwashers.

BACKGROUND OF THE INVENTION

A traditional centrifugal pump comprises a pump body having a motor and a pump head connected to the pump body. The pump head comprises a chamber and an impeller received inside the chamber. The chamber is provide with an inlet and an outlet. When the impeller is rotated by the motor, liquid is pushed radially outwardly by the impeller which forces the liquid out the outlet and creates a low pressure area at the center of the impeller that draws liquid into the chamber through the inlet.

The motor is usually a brushless motor, comprising a stator and a rotor rotatably mounted to the stator. The stator comprises a stator core and stator windings wounded about teeth of the stator core. The rotor comprises a shaft, a rotor core fixed onto the shaft and permanent magnets fixed onto the rotor core. One end of the shaft passes into the pump head to drive the impeller.

One disadvantage of the prior centrifugal pump is that, heat generated by the stator will affect the reliability and efficiency of the motor.

SUMMARY OF THE INVENTION

Thus there is a desire for a pump having a motor with improved heat dissipation such that heat generated by the motor will not adversely affect the operation of the pump.

Accordingly, in one aspect thereof, the present invention provides a centrifugal pump comprising: a pump body incorporating a motor, the motor comprising a stator and a rotor rotatably mounted to the stator, the stator comprises a stator core and windings and the rotor comprises a shaft; a pump head mounted to the pump body, the pump head comprising a volute and an impeller disposed within the volute; the volute forming a chamber having an inlet and an outlet; the chamber has an opening facing the pump body; wherein the motor comprises an end cap made of thermally conductive material and mounted to an axial end of the stator core, the end cap comprising an annular sidewall disposed around the stator core and a base plate connected with the annular sidewall, the base plate covering the opening of the chamber to transfer heat generated by the stator to liquid inside the chamber.

Preferably, the opening of the chamber is sealed by the base plate.

Preferably, the base plate and the annular sidewall are formed as a monolithic structure.

Preferably, the end cap comprises a hub having a bearing supporting the shaft.

Preferably, the base plate has a stepped recess accommodating a rotatable seal between the base plate and the shaft.

Preferably, the hub forms a compartment open toward the rotatable seal and a water slinger is fixed to the shaft and disposed within the compartment and a channel connects the compartment with a drain hole formed in the sidewall.

Preferably, the outer surface of the annular sidewall is provided with a thermal insulating layer.

Preferably, the pump body is further provided with an annular shield surrounding the outer surface of the annular sidewall.

Preferably, the end cap is provided with a thermal insulating layer disposed between the annular shield and the annular sidewall.

Preferably, both the annular sidewall and the connection between the annular sidewall and the base plate are airtight.

Preferably, a part of an outer surface of the stator core is covered by the annular sidewall and another part of the outer surface of the stator core is exposed to the air.

Preferably, an axial end of the annular sidewall remote from the base plate is formed with a step in its inner surface and the stator core mates with the step.

According to a second aspect, the present invention provides a kitchen appliance comprising: an inlet pipe; an outlet pipe; a circulation path; and a centrifugal pump according to the first aspect above, wherein the pump is arranged to heat a liquid while moving the liquid along the circulation path.

Preferably, the kitchen appliance is a dishwasher.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below.

FIG. 1 illustrates a centrifugal pump according to a first embodiment of the present invention;

FIG. 2 is a sectional view of the centrifugal pump of FIG. 1;

FIG. 3 shows an annular wall, being a part of the centrifugal pump of FIG. 1;

FIG. 4 is a sectional view of a centrifugal pump according to a second embodiment of the present invention;

FIG. 5 is a sectional view of a centrifugal pump according to a third embodiment of the present invention;

FIG. 6 is a view of a part of the centrifugal pump of FIG. 5;

FIG. 7 is a sectional view of a centrifugal pump according to a fourth embodiment of the present invention; and

FIG. 8 is a schematic view of a dishwasher applying the centrifugal pump according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1, 2 and 3, the centrifugal pump 10 in the first embodiment of the present invention comprises a pump head 20 and a pump body 40 connected to the pump head 20. The pump body 40 comprises a motor having a stator and a rotor rotatably mounted to the stator, via bearings 66, 68. The stator comprises a stator core 42 having annular yoke portion and teeth extending inwardly from the yoke portion, stator windings 43 wounded onto the teeth of the stator core 42 and two end caps 44, 46 that are respectively mounted to two ends of the stator core 42. In this embodiment, the stator core 42 and end caps 44, 46 are mounted together by axial screws that axially pass through the two end caps 44, 46 and/or the stator core 42. The rotor comprises a shaft 62, a rotor core 64 fixed onto the shaft 62. In the embodiments shown, the illustrated motor is an induction motor but any other motor may be used. The pump head 20 comprises a volute 22 and an impeller 28 disposed within the volute 22. The volute 22 comprises a chamber 30 having an inlet 24 and an outlet 26. Chamber 30 has with an opening facing the pump body 40. When the centrifugal pump is operating, the impeller is rotated by the motor, creating a low pressure area at the impeller center, which draws liquid into the volute 22 through the inlet 24. The liquid flows out of the volute through the outlet 26, under pressure.

In this embodiment, the end cap 46 is made of thermally conductive material. The end cap 46 comprises a base plate 48 and an annular sidewall 47 that extends from the outer peripheral of base plate 48. The annular sidewall 47 stands on and is disposed around one end of the stator core 42. Heat transfers from the stator core 42 to the annular sidewall 47. The base plate 48 is mounted to the volute 22 to seal the opening of chamber 30. To this end a rubber O-ring 54 is squeezed between the base plate and the volute. In the area defined by the chamber opening, the base plate 48 is thermally conductively exposed to the liquid (such as water) in the chamber to transfer heat generated by the stator core 42 to the liquid in the chamber. The base plate 48 is further provided with a recess or stepped portion forming a seat 51 for mounting a rotatable seal 50 to make the connection between base plate 48 and shaft 62 water-tight.

In this embodiment, the base plate 48 and annular sidewall 47 are separately formed with the base plate 48 connected to one end of annular sidewall 47, both mechanically and thermally, such that heat can be transferred between annular sidewall 47 and base plate 48. The annular sidewall 47 comprises a plurality of spokes 53 extending inwardly and a hub 52 supported by inner ends of the spokes 53. The hub forms a bearing housing and accommodates bearing 66 for rotatably supporting the impeller end of the shaft. The other end cap has the other bearing 68 for supporting the other end of the shaft. Optionally, the bearing is water-proof to avoid damage should liquid in the chamber of volute 22 leak into the motor.

The heat generated by stator core 42 and/or stator windings 43 is transferred to liquid in chamber 30 via the heat-conducting end cap 46, which allows the heat from the stator to be dissipated quickly. Furthermore, the transferred heat may raise the temperature of the liquid to recycle or reuse the heat. This invention is especially suitable for applications in which the liquid being pump also needs to be heated, such as certain kitchen appliances, and in particular, a dishwasher.

Optionally, hub 52 is formed with a compartment 72 open towards seal 50. Disposed within this compartments is a water slinger fixed fast to shaft 62. A channel 74 runs from the compartment to a drain hole 76 in the sidewall. Thus should water leak passed rotary seal 50 along shaft 62 it will by flung off the shaft by slinger 70 into compartment 72 and then drain from the motor along channel 74 and out of the motor via drain hole 76. It is preferable that the motor when mounted for use, is orientated such that water will flow out along the channel under gravity.

In the second embodiment, as shown in FIG. 4, the pump body 40 is further provided with an annular shield 55 surrounding the outer surface of annular sidewall 47. Annular shield 55 reduces or eliminates the heat dissipating from annular sidewall 47 to air, so that most of the heat generated by the stator core 42 and/or the stator windings 43 is transferred to the liquid in chamber 30, via annular sidewall 47 and base plate 48.

As shown in FIGS. 5 and 6, in the third embodiment, the end cap 46 is provided with a thermal insulating layer 57 disposed between annular shield 55 and annular sidewall 47. Preferably, the thermal insulating layer covers the outer surface of annular sidewall 47. The thermal insulating layer further reduces or eliminates the dissipation of heat from annular sidewall 47 to air, so that most of the heat generated by the stator core 42 and/or the stator windings can be transferred from the annular sidewall 47 to the liquid in the chamber 30 via base plate 48. Alternatively, it is possible to apply thermal insulating layer 57 to the pump according to the embodiment shown in FIG. 2. That is, in the absence of an annular shield, a thermal insulating layer could be arranged to cover annular sidewall 47.

As shown in FIG. 7, in the fourth embodiment, base plate 48 and annular sidewall 47 are formed as one single piece, i.e. as a monolithic structure. By reducing the number of components the centrifugal pump is easier to assemble. Compared with the first embodiment, the fourth embodiment of FIG. 7 eliminates the need for the spokes, with hub 52 being supported by base plate 48. In addition, one end of annular sidewall 47 is provided with a step 49 in its inner surface. Step 49 contacts both an axial end surface and an outer surface of stator core 42. By using the step configuration, it is easy to mount end cap 46 to stator core 42. The step design may be applied to the other end cap 44.

In the aforesaid embodiments, a part of the outer surface of the stator core 42 is covered by end caps 44 and 46, the other part of the outer surface is exposed to the air. Alternatively, all of the outer surface of stator core 42 could be completely covered by the annular sidewalls of end caps 44 and 46.

In the aforesaid embodiments, the annular sidewall of the other end cap 44 is provided with some through-holes 45 (see FIG. 1) interconnecting the interior of the motor with the air outside the motor, to help heat dissipation.

Preferably, annular sidewall 47 of end cap 46 is airtight (without any through-holes). The connection between annular sidewall 47 and base plate 48 is also airtight. As such, end cap 46 covers the stator core 42 like a thermally conductive cup. The heat generated by stator core 42 and/or stator windings 43 can be transferred to end cap 46 by means of radiation, air thermal conduction and direct thermal conduction, and is transferred to the liquid in volute 22 through base plate 48. In addition, the airtight annular sidewall and the airtight connection assist in gathering and transferring the heat.

As shown in FIG. 8, a dishwasher 110 according to another embodiment of the present invention comprises: a washing chamber 112, an inlet pipe 114 for supplying washing water to the cleaning chamber 112, an outlet pipe 116 with a drainage pump 122 for discharging washing water, a circulation path 118 with a circulating pump 124, and a control system 120 for controlling drainage pump 122 and circulating pump 124. The drainage pump 122 removes the washing water from cleaning chamber 112 via outlet pipe 116. The circulating pump 124 pumps washing water from cleaning chamber 112 along circulation path 118 for circulating the washing water. The centrifugal pump according to the aforesaid embodiments can be used as the circulating pump 122. Thus the washing water is being heated by the pump as the water is being circulated. An additional heater may be needed to heat the washing water to the required temperature but due to the heat provided by the pump the heater uses less energy to attain and maintain the required temperature.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item or feature but do not preclude the presence of additional items or features.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims. 

1. A centrifugal pump comprising a pump body incorporating a motor, the motor comprising a stator and a rotor rotatably mounted to the stator, the stator comprises a stator core and windings and the rotor comprises a shaft; a pump head mounted to the pump body, the pump head comprising a volute and an impeller disposed within the volute; the volute forming a chamber having an inlet and an outlet; the chamber has an opening facing the pump body; wherein the motor comprises an end cap made of thermally conductive material and mounted to an axial end of the stator core, the end cap comprising an annular sidewall disposed around the stator core and a base plate connected with the annular sidewall, the base plate covering the opening of the chamber to transfer heat generated by the stator to liquid inside the chamber.
 2. The centrifugal pump of claim 1, wherein the opening of the chamber is sealed by the base plate.
 3. The centrifugal pump of claim 1, wherein the base plate and the annular sidewall are formed as a monolithic structure.
 4. The centrifugal pump of claim 1, wherein the end cap comprises a hub having a bearing supporting the shaft.
 5. The centrifugal pump of claim 1, wherein the base plate has a stepped recess accommodating a rotatable seal between the base plate and the shaft.
 6. The centrifugal pump of claim 5, wherein the hub forms a compartment open toward the rotatable seal and a water slinger is fixed to the shaft and disposed within the compartment and a channel connects the compartment with a drain hole formed in the sidewall.
 7. The centrifugal pump of claim 1, wherein the outer surface of the annular sidewall is provided with a thermal insulating layer.
 8. The centrifugal pump of claim 1, wherein the pump body is further provided with an annular shield surrounding the outer surface of the annular sidewall.
 9. The centrifugal pump of claim 8, wherein the end cap is provided with a thermal insulating layer disposed between the annular shield and the annular sidewall.
 10. The centrifugal pump of claim 1, wherein both the annular sidewall and the connection between the annular sidewall and the base plate are airtight.
 11. The centrifugal pump of claim 1, wherein a part of an outer surface of the stator core is covered by the annular sidewall and another part of the outer surface of the stator core is exposed to the air.
 12. The centrifugal pump of claim 1, wherein an axial end of the annular sidewall remote from the base plate is formed with a step in its inner surface and the stator core mates with the step.
 13. A kitchen appliance comprising: an inlet pipe; an outlet pipe; a circulation path; and the centrifugal pump of claim 1, wherein the pump is arranged to heat a liquid while moving the liquid along the circulation path.
 14. The kitchen appliance of claim 13, wherein the annular sidewall is in thermal contact with the stator core.
 15. The kitchen appliance of claim 13, wherein the end cap comprises a hub having a bearing supporting the shaft.
 16. The kitchen appliance of claim 13, wherein the base plate has a stepped recess accommodating a rotatable seal between the base plate and the shaft.
 17. The kitchen appliance of claim 16, wherein the hub forms a compartment open toward the rotatable seal and a water slinger is fixed to the shaft and disposed within the compartment and a channel connects the compartment with a drain hole formed in the sidewall.
 18. The kitchen appliance of claim 13, wherein the outer surface of the annular sidewall is provided with a thermal insulating layer.
 19. The kitchen appliance of claim 13, wherein the pump body is further provided with an annular shield surrounding the radially outer surface of the annular sidewall.
 20. The kitchen appliance of claim 19, wherein the end cap is provided with a thermal insulating layer disposed between the annular shield and the annular sidewall.
 21. The kitchen appliance of claim 13, wherein an axial end of the annular sidewall remote from the base plate is formed with a step and the stator core mates with the step.
 22. The kitchen appliance of claim 13, wherein the kitchen appliance is a dishwasher. 